Printed circuit boards or multilayer circuit boards (which comprise several printed circuit boards in layers) are used in many electronic devices. A printed circuit board is a support made of insulating material with adherent conducting connections. It is used for the mechanical fixing and electrical connection of electronic circuit components and parts. Integrated circuits can be placed directly on or in the printed circuit board. In a multilayer circuit board, such printed circuit boards are connected to each other electrically and/or mechanically.
Short-circuits on such printed circuit boards or in a multilayer circuit board may lead to malfunctions. For example, short-circuits caused by moisture penetrating the housing of the electronic circuit, may result in the unintended activation of an electrically controlled component. This problem is becoming apparent more frequently in view of the increasing electronification of motor vehicles. One example of this is an electronic parking brake, in which the relevant control electronics are arranged in or on the actuator.
Voltage-controlled components are found to be highly sensitive to short-circuits with a corresponding operating potential. For example, if a short-circuit occurs in a circuit for controlling an electronic parking brake (EPB) in a land vehicle, wherein said short-circuit has an operating potential which corresponds to that of the EPB, the EPB is unintentionally activated. This could be particularly critical to safety if the brake is released while in parked mode or applied while the vehicle is being driven.
A known method of detecting a short-circuit on a printed circuit board is for active protective circuits to be mounted on the printed circuit board for regions with supply voltage potential. An active protective circuit includes an electronic evaluation unit, which monitors parameters such as voltage, current and temperature, for example. Circuit components, parts and groups arranged on the printed circuit board are then brought to a safe state depending on the measurements of the electronic evaluation unit. This may prevent a malfunction or an unintended activation of, or damage to, downstream components by a short-circuit current, which is usually significantly higher than the operating current.
DE 198 54 914 A1 describes a method and a circuit arrangement for detecting a fault, in particular a short-circuit, in the load circuit of a controlled power switch. The start of regulation of the load current limitation in the controlled power switch is used as a measure for a short-circuit.
However, if a number of short-circuits occur in parallel, the protection facilities described therein do not provide adequate protection.